The invention relates generally to fiber optic lighting systems, and more particularly to fiber optic lighting system connectors therefor.
Fiber optic lighting systems are known and include generally one or more fiber optic cables for transmitting visible light from a source to one or more environment illuminating fixtures. The light is typically emitted from a halogen, or metal halide, or a broad spectrum source, and is transmitted through one or more fiber optic cables having a light transmitting core covered by an outer coaxial cladding, whereby the refractive index of the core is greater than that of the cladding to internally reflect light transmitted therethrough. In some fiber optic cables, the core is a PMMA material and the cladding is a TEFLON material. The cladding is usually covered by a protective coaxial outer sheath, or jacket, and may include a yarn or other strengthening material therebetween. Fiber optic cables suitable for lighting system applications have a diameter in a range generally between approximately 2 mm and approximately 25 mm, although the diameter may be more or less depending on the particular application requirements. The light fixtures include generally lenses and other devices coupled to the fiber optic cable for emitting, and sometimes diffusing, light where desired. In some applications, the fiber optic cable itself is oriented or modified to emit light directly therefrom, for example from an end portion thereof, or from exposed portions of the core along its axial length.
Fiber optic lighting systems have many advantages over conventional lighting systems, and are an attractive alternative for many applications. A single light source in a fiber optic lighting system may supply light through multiple fiber optic cables coupled to corresponding light emitting fixtures. This configuration has great potential for substantially reducing maintenance associated with changing multiple light bulbs required in conventional lighting systems. In aircraft passenger cabins, for example, a single light source located in a readily accessible equipment bay may power multiple overhead or aisle or other cabin light fixtures, thereby eliminating laborious and costly disassembly of interior panels required to replace conventional light bulbs.
Fiber optic lighting systems are also capable of isolating heat and undesirable wavelengths, particularly those in the ultraviolet portion of the spectrum, from the light emitting fixture. Thus fiber optic lighting systems are useful in applications where it is desirable to eliminate heat generated by conventional lighting systems, and in applications where ultraviolet radiation is a concern. For example, heat and ultraviolet radiation generated by conventional lighting systems may adversely affect food products illuminated thereby resulting in melting or early spoilage thereof. Fiber optic lighting systems are also useful in applications where it is desirable to isolate electrical equipment from the illuminated environment to reduce electromagnetic interference and to eliminate electrical hazards, for example in the illumination of swimming pools and other water bodies. Fiber optic lighting systems are also desirable for many other applications.
The potential application of fiber optic lighting systems however remains largely unrealized in part for inefficiencies associated with the transmission of power between the light source and the light emitting fixtures. Some power loss occurs as light propagates along the axial length of the fiber optic cable, and it is estimated that existing commercially available fiber optic cables lose approximately 2 percent of the transmitted power per linear foot of cable. Advances in materials science however are expected to substantially reduce these losses in the near future. Another source of power loss in fiber optic lighting systems, and that with which the present invention is concerned primarily, is associated with the mechanical coupling of fiber optic cables generally, and more particularly the connecting of fiber optic cables to light sources, and to other fiber optic cables, and to light emitting fixtures.
Known fiber optic lighting system connectors include the application of an epoxy, or more generally an adhesive, and/or shrink wrap materials about abutting fiber optic cable end portions. The application of adhesive however is time consuming and usually requires an assembly device to temporarily hold the cable end portions in axially abutting alignment until the adhesive hardens. The application of adhesive may also require heat or a radiation source to facilitate curing. Adhesives do have the advantage of filling gaps between the abutting cable portions, which tend to have relatively rough surfaces that otherwise reduce the efficacy of power transmission thereacross. Adhesives however often have different refractive properties, or indices, than fiber optic cables and conductor members of the light source and fixture, resulting in additional power loss, which is undesirable.
Shrink wrapping abutting end portions of fiber optic cables is less costly and time consuming than some adhesive couplings, but shrink wrapped couplings are generally relatively lossy since abutting cable end portions have a tendency to separate axially, thereby forming air gaps therebetween, which are a significant source of power loss. Shrink wrap materials are used often in combination with adhesives. However, neither shrink wrap nor adhesives are reusable since the coupling formed thereby must usually be destroyed to disassemble the fiber optic cable end portions, which may be damaged also.
Other known prior art connectors used in fiber optic lighting systems include adaptations from other technologies, which perform only marginally well. The SKINTOP II liquid tight strain relief cord connector available from Olflex Wire & Cable, Inc. Fairfield, N.J., for example, has been employed to couple fiber optic cables to light sources. The SKINTOP II connector includes generally a collet disposed about the fiber optic cable, and a sealing nut disposed about the cable and engaged with a first threaded outer surface portion of the collet. A tapered surface of the sealing nut urges axial finger members of the collet radially inwardly into clamping engagement with the fiber optic cable. A second outer threaded surface portion of the collet is coupled to the light source, thereby holding the fiber optic cable in abutting relation relative to a mating light conducting portion.
The SKINTOP II connector is designed for electrical applications, and includes a sealing member between the finger members and the fiber optic cable disposed therethrough. The SKINTOP II connector however does not bias the end portion of the fiber optic cable axially toward and into engagement with the mating end portion of the light source. Absent such an axial bias, it is not possible to eliminate power reducing air gaps, or occlusions, formed between the end of the fiber optic cable and the mating end portion of the light source when the SKINTOP II is used in fiber optic lighting systems.
Other known prior art connectors adapted from other technologies for use in fiber optic lighting systems include a multiple-component pneumatic conduit connector available from the John Guest Company, Madison, Wis. This connector includes a body member having a bore therethrough for accommodating mating conduit end portions and portions of a corresponding collet disposed thereabout. The collets have several metal teeth formed in corresponding flexible fingers thereof which bite into the conduits. The metal teeth are required apparently to engage either metal or plastic fluid conduits coupled by the connector. For this purpose, a c-shape spring clip disposed between an outer flange of the collet and an end portion of the body member urges the collet axially outwardly from the bore of the body member, thereby engaging the teeth of the finger members with the conduit. As the collet is drawn axially out the body member by the spring clip, however, so too is the conduit engaged by the teeth thereof, resulting in formation of an air gap between the end portions of abutting conduits. Thus, the John Guest connector does not axially bias the conduit end portions into mating engagement. The John Guest connector also includes an o-ring disposed between each conduit and the body member to form a fluid tight seal between the abutting end portions thereof, so that any spacing between the conduit end portions is not a concern in fluid coupling applications, for which the John Guest connector was designed. In fiber optic cable coupling applications, however, the John Guest connector provides a less than desirable coupling for its inherent tendency to form air gaps between abutting fiber optic cable portions. The John Guest connector is also relatively costly to manufacture, due in part to the metal teeth which must be formed in the plastic collet by insert molding or other means, and in part due to the many components and required assembly thereof.
U.S. Pat. No. 5,668,904 issued Sep. 1, 1997 to Sutherland et al. and entitled "Fiber Optic Cable Connector Apparatus and Method" discloses a communications fiber optic cable connector frame designed to mate with a communications industry standard connector block. A fiber optic cable is disposed coaxially in a grooved or threaded bore of a retaining collet, and the retaining collet has a threaded outer surface disposed in a threaded bore of the connector frame. An unthreaded tapered portion of the bore in the connector frame applies a radially inwardly directed force on the retaining collet as the collet is engaged therewith, to resist tension forces that tend to separate the fiber optic cable therefrom. A compressed spring disposed about an end portion of the connector frame and acting between a radial flange thereof and a cap disposed axially thereabout biases the connector frame and the fiber optic cable retained therein toward the connector block. The connector frame however is relatively complex for its many components, particularly the cap and spring assembly required to axially bias the cable toward the connector block, and is costly to manufacture. Moreover, the connector frame of U.S. Pat. No. 5,668,904 was designed specifically for coupling with a communications industry standard connector block.
The present invention is drawn toward advancements in the art of fiber optic lighting systems, and more particularly to fiber optic lighting system connectors therefor, and combinations thereof.
An object of the invention is to provide novel connectors for fiber optic lighting systems and combinations thereof that overcome problems in the prior art.
Another object of the invention is to provide novel fiber optic lighting system connectors having any one or more advantages over the prior art, including improved power transmission efficiency, improved economy, relative ease of assembly and disassembly, fewer components, reduced complexity, elimination of adhesives or epoxies, elimination of special tools for assembly, among other advantages.
A further object of the invention is to provide novel fiber optic lighting system connectors having one or more caps non-threadably coupled to a sleeve member, and movable axially relative thereto to axially retain a fiber optic cable end portion in the sleeve member.
Another object of the invention is to provide novel fiber optic lighting system connectors that apply and maintain an axially bias on a fiber optic cable end portion toward another fiber optic cable end portion or toward a conductor member of a light source or a light fixture retained or biased axially in an opposing direction to provide an improved coupling therebetween.
Another object of the invention is to provide novel fiber optic lighting system connectors having a coupling medium disposable between a fiber optic cable end portion and a conductor member to provide improved light transmission therebetween, and a related object of the invention is to provide a unitary coupling medium that also provides a seal between the connector and the fiber optic cable end portion and conductor member.
Still another object of the invention is to provide novel fiber optic lighting system connectors useable for coupling a fiber optic cable to a conductor member comprising generally a sleeve member having a plurality of resilient fingers and an axial bore for receiving the fiber optic cable and conductor member, and one or more caps non-threadably coupled to corresponding end portions of the sleeve member. Each cap is movable axially relative to the sleeve member between first and second positions to constrict the plurality of resilient fingers about a fiber optic cable or conductor member disposed in the axial bore thereof.
It is yet another object of the invention to provide novel fiber optic lighting system connectors having an improved sleeve member with a plurality of resilient fingers one or more of which have a corresponding tooth formable in a molding operation without damage to the tooth upon separation of a mold core.
These and other objects, aspects, features and advantages of the present invention will become more fully apparent upon careful consideration of the following Detailed Description of the Invention and the accompanying Drawings, which may be disproportionate for ease of understanding, wherein like structure and steps are referenced generally by corresponding numerals and indicators.